Zotero [zoh-TAIR-oh] is a free and easy-to-use tool to help you collect, organize, cite, and share your research sources. It's an open-source project housed at the Roy Rosenzweig Center for History and New Media at George Mason University and the Corporation for Digital Scholarship.
Zotero collects all your research in a single, searchable interface. You can add PDFs, images, audio and video files, snapshots of web pages, and anything else you can think of that you might need to cite down the line.
Thanks to Wake Forest University's Zotero guide for this introduction!